This invention relates in general to imaging systems, and more specifically, concerns a novel migration imaging system.
There has recently been developed a migration imaging system capable of producing images of high quality and excellent resolution. This system is described in detail and claimed in copending application Ser. No. 460,377, filed June 1, 1965, now U.S. Pat. No. 3,520,681; Ser. No. 837,591, filed June 30, 1969; and Ser. No. 837,780, filed June 30, 1969. In a typical embodiment of this imaging system, an imaging member is prepared by coating a layer of a softenable material, for example a soluble insulating resin, onto a supporting substrate and overcoating the softenable layer with a fracturable layer of migration marking material which in this particular embodiment comprises a layer of electrically photosensitive material. This imaging member is electrically latently imaged, for example, by electrostatically charging the surface of the member with a corona discharge device, and exposing the member to an image pattern of activating electromagnetic radiation, here light. The latently imaged member is then developed by softening the softenable layer, for example by applying a solvent for the softenable material, which in addition to softening the layer may also dissolved it. Portions of the fracturable layer of migration marking material which have been exposed migrate through the softenable layer as it softens or dissolves leaving an image pattern of migration marking material on the substrate conforming to a negative of a positive original image. Those portions of the fracturable layer which do not migrate toward the substrate (here those portions which were not exposed to light) and substantially all of the softenable layer are washed away by the solvent. The image left on the substrate is of high quality and good resolution. Various alternative embodiments are further described in the above cited copending applications.
"Softenable" as used herein is intended to mean any material which can be rendered more permeable thereby enabling particles to migrate through its bulk. Conventionally, changing permeability is accomplished by heat or solvent softening. "Fracturable" layer or material as used herein, means any layer or material which is capable of breaking up during development, thereby permitting portions of said layer to migrate towards the substrate or to be otherwise removed.
Another recently developed migration imaging system utilizes photosensitively inert particles in an imaging structure such as that described above. This system is described in detail in copending application Ser. No. 483,675, filed Aug. 30, 1965. In this system the imaging member is laterally imaged directly, for example, by corona charging through a stencil or mask. When the softenable material layer is developed and dissolved by dipping the plate in the solvent for said softenable layer, migration marking particles migrate toward the substrate in imagewise configuration. Undesired and unmigrated marking particles are typically washed away along with substantially all of the softenable layer. While this imaging process does not require photosensitive or photoconductive materials (although they may be used herein with equally acceptable results) the charge pattern must typically be originally applied in image configuration, e.g., by corona charging through a stencil. The image produced by this process has a similar appearance to those produced by the migration imaging system already described above.
In new and growing areas of technology such as the migration imaging system of the present invention, new methods, apparatus, compositions, and articles of manufacture are often discovered for the application of the new technology in a new mode. The present invention relates to a novel migration imaging system having novel migration imaging members including surface skin layers at the surface of the softenable material.